TheSamba.com :: View topic - Wiring a center speaker off the left and right speakers.

Mon Jun 05, 2017 10:05 am

Rather than spend money on speakers that will have no bass response I'm going to use small box speakers left over from a surround system.
They fit nice under the dash...
I want to wire the center channel in off the two side speakers.

Is this the right wiring config?

Mon Jun 05, 2017 10:53 am

You might do well to search or ask this at DIYMA.

http://www.diymobileaudio.com/forum/

But be prepared for a good dose of audio snobbery ;)

Mon Jun 05, 2017 11:10 am

This is possibly not what you're asking but, I wired a '70's radio with a mono output up to the central dash speaker and two smaller units in the doors. They were all 4ohm speakers. To aVoid too low a resistance for the single radio output I wired the two door speakers in series and wired that pair in parallel with the central speaker. The overall resistance is then just under 3 ohms.
I suspect you have a head unit with separate outputs, so probably not a relevant suggestion!

Mon Jun 05, 2017 11:12 am

Chad1376 wrote: You might do well to search or ask this at DIYMA.

http://www.diymobileaudio.com/forum/

But be prepared for a good dose of audio snobbery ;)
That's why I posted here.
But this is fairly simple.

When dealing with old cars, old volvos, mercedes vw... replacing the speakers is always disappointing.
So this time I put some full range speakers from home system under the rear deck. I'll replace the deck top with something permeable but finished looking.
I'll mount these u set the dash with some kick ass Velcro and call it a day.
I might add a bass limiting filter for the front channel that cruthfield sells for about $10 and just gets spliced into the line. But these little guys might already be made to limit bass.
So far it sounds good with just he back speakers.

Mon Jun 05, 2017 11:20 am

You need a stereo to mono summing circuit to do it properly, the scheme you show will not work properly for some stereos. Best to do it at signal level and then run it into a separate amplifier channel for the speaker.

Mon Jun 05, 2017 11:27 am

I'm have more home theater audio experience than with cars, but with music in a car, it is recorded in stereo (left and right). Adding in a "center channel" isn't going to help. This isn't a 5.1 home theater system.

When adding multiple speakers onto an amp's terminals (in parallel or series), you have to make sure the amp can handle the ohm load. If your amp could handle it, you could add the "center" off of the left or right speaker, but I wouldn't recommend that. Stick with stereo.

Mon Jun 05, 2017 12:01 pm

By "center channel" I'm assuming you actually want that single large speaker to be your subwoofer? And the bass from both the left and right sides will pass to this single speaker, right? And you are NOT trying to make a "center front channel" like you would find on a 5.1 system?

It's been a few years since I wired a car audio system, but I'd say that won't work as you have it in the diagram. For two reasons...
1) The speaker output from the head are expecting speakers of a consistent resistance (usually 4-ohms per channel for car audio). Chaining speakers together will increase the resistance. But also, many home speakers (which is what I guess you are using for the center speaker) are 8-ohm speakers.

2) The way you have it wired, that center/sub speaker would become a 2nd left speaker.

What you have diagramed above looks almost like bridged output from an stereo amplifier. Many amps allow the stereo outputs to be bridged together to form a single channel output of twice the power. This is meant to drive a subwoofer. Usually, these will also have a built-in crossover unit to filter out the high frequencies which "muddy" the subwoofer sounds. I've not heard of a head unit that allowed this type of wiring (except maybe for some early Sony units).

You might be able to utilize the pre-amp outputs from your head unit (assuming it has this) to power a small amplifier and bridge the output of this amp to power your single speaker. Use the head unit's powered speaker outputs to run the two full range speakers.
You might also want to look into some high pass filters (or crossovers) to filter out the low frequencies from the smaller speakers leaving the bass to the single sub.

Mon Jun 05, 2017 2:49 pm

I studied this stuff for ages figuring out how to command a mono speaker from a stereo that had amplified output only by summing the signal as the internal amp of my HU did not take bridging well. even draw up some circuitry with help from a colleague who works in electronics... but in the end I decided it was a lot easier to keep it as simple as possible:

https://www.thesamba.com/vw/forum/viewtopic.php?t=617633

Mon Jun 05, 2017 3:11 pm

I guess I'm just calling it a center channel.

What I'm thinking would happen is that each side would get stereo and the center would get a mix.

When I ran a kicker in my old Volvo station wagon I just wired the positive for the left and the neg from the right.

I can't find the center channel speaker from the home theater system any way.

I'll just run the two sides.

Mon Jun 05, 2017 3:20 pm

Thank God in Heaven. You were inches from creating a hellish sonic vertigo.

Remember what Damien Thorn did to his cousin Mark in the woods on "Damien: The Omen II?" That's what it would have felt like.

Mon Jun 05, 2017 3:29 pm

Here is a pic from the Crutchfield page on Subwoofers:

https://www.crutchfield.com/S-kNP7x97Rtr8/learn/learningcenter/car/subwoofers_faq.html

Notice the two terminals marked as "bridged". This amp was designed to be used with a single speaker being driven by the left and right sides of the amp.

Give the page above a read it is exactly what you are looking for.

FYI, I do recall some home stereo/surround systems will send the L and R channels from the amp/receive thru the subwoofer first before splitting out to the left and right sides. The subwoofer itself took care of combining the signals.

If you have one of these speakers you might be able to use it, but still need to understand if the head unit can drive ALL three speakers (speaker impedance). Again, read the link above to get an understanding of impedance.

Mon Jun 05, 2017 4:14 pm

Cool. Thank you.

Actually, I'm not trying to use the bridged center speaker as a sub.

Just to get a fuller sound. But its a moot issue beacuse I cannot find that speaker anyway.

I already have some decent bass coming from the rear home speakers.

the home speakers are 8 ohms.

Mon Jun 05, 2017 5:51 pm

chrisarnt wrote: Cool. Thank you.

Actually, I'm not trying to use the bridged center speaker as a sub.

Just to get a fuller sound. But its a moot issue beacuse I cannot find that speaker anyway.

I already have some decent bass coming from the rear home speakers.

the home speakers are 8 ohms.

Nothing really wrong per se in using home stereo speakers in the car- just be aware that using 8 ohm speakers with a 4 ohm car stereo will decrease the dynamic output capability of the stereo.
For example, in a perfect world, with a car stereo that puts out 60 watts per channel (continuous power) into 4 ohms, a 4 ohm speaker will see 60 watts. But an 8 ohm speaker in that situation would only see 30 watts. By doubling the resistance of the speaker, you are halving the wattage the speaker sees. (In the real world it doesn't exactly work like this but it's a close enough measurement for our scenario here.)
Will that 30 watts difference make any real difference in perceived volume? Probably not enough that can't be compensated by just adjusting the volume a bit. But it does make a difference in dynamic speaker output- the bass of the speaker will have a bit less "slam" and the treble a bit less "ring" to it. However if it sounds good to you that's all that matters.

Mon Jun 05, 2017 6:44 pm

For a L,R, and center set-up, run a wire from the positive of each side to the center speaker ( one to the pos lead, one to the neg lead. No neg wire involved).. This will give you the "stereo difference" to the center speaker. It will work best with the balance control in the middle.
For a front/rear ( or four-speaker) set-up, you can take the positives off of the rear channels and feed them to the center.
You will still get the stereo difference, and the center speaker is controlled by the fader.

I have done this many times. It is best with LIVE recorded music, tho.
Really fills out the sound.

Mon Jun 05, 2017 7:06 pm

rastomas wrote: For a L,R, and center set-up, run a wire from the positive of each side to the center speaker ( one to the pos lead, one to the neg lead. No neg wire involved).. This will give you the "stereo difference" to the center speaker. It will work best with the balance control in the middle.
For a front/rear ( or four-speaker) set-up, you can take the positives off of the rear channels and feed them to the center.
You will still get the stereo difference, and the center speaker is controlled by the fader.

I have done this many times. It is best with LIVE recorded music, tho.
Really fills out the sound.

Hafler Matrix.

I design and build audio gear, and have a few ways to do this at line level, but it's a neat trick on some amps and stereos to get that immersive feeling to the sound. Many old jukeboxes did this as well to get a more lively and full immersive experience. Works pretty well. Great for 70's and 80's recordings usually from live venues

Mon Jun 05, 2017 7:45 pm

The effect does create a bit of a "stage" but the method only works with the advantages of space and listening distance. The ability to tune the environment is key. With a driver consuming half the soundstage and dispersion of the passenger side speaker already having an advantage from the listening perspective- I still believe the experience would make birds migrate 6 months early and every neighborhood dog would no longer sniff each other.

Mon Jun 05, 2017 8:19 pm

rastomas wrote: For a L,R, and center set-up, run a wire from the positive of each side to the center speaker ( one to the pos lead, one to the neg lead. No neg wire involved).. This will give you the "stereo difference" to the center speaker. It will work best with the balance control in the middle.
For a front/rear ( or four-speaker) set-up, you can take the positives off of the rear channels and feed them to the center.
You will still get the stereo difference, and the center speaker is controlled by the fader.

I have done this many times. It is best with LIVE recorded music, tho.
Really fills out the sound.

Doesn't this cause the center speaker to be out of phase? This is why receivers that allow center and sub mono signals to be used in stereo surround situations have time delay and phase controls.

Mon Jun 05, 2017 9:16 pm

sb001 wrote: rastomas wrote: For a L,R, and center set-up, run a wire from the positive of each side to the center speaker ( one to the pos lead, one to the neg lead. No neg wire involved).. This will give you the "stereo difference" to the center speaker. It will work best with the balance control in the middle.
For a front/rear ( or four-speaker) set-up, you can take the positives off of the rear channels and feed them to the center.
You will still get the stereo difference, and the center speaker is controlled by the fader.

I have done this many times. It is best with LIVE recorded music, tho.
Really fills out the sound.

Doesn't this cause the center speaker to be out of phase? This is why receivers that allow center and sub mono signals to be used in stereo surround situations have time delay and phase controls.

Yup. Properly done you need a time delay and some phase shift to do it, unless the rear difference signal is being sent to speakers that are physically pretty far away.

In my opinion it belongs in the home theatre/listening room sort of setup

Tue Jun 06, 2017 8:04 am

It sounds like the OP isn't going to do a center now, but since we're on the subject, here's a cool doo-dad that would accommodate all of the above. I've used them on several projects. You could sum the two stereo channels into a center, apply phase and time delay correction, and even have another mono channel for a sub-out. Active crossovers + parametric EQ also. Of course you'd need a line converter if the deck doesn't have RCA out, and appropriate amplifier(s) on the other end.

https://www.minidsp.com/products/minidspkits/2-x-in-4-x-out

Tue Jun 06, 2017 4:11 pm

Lingwendil wrote: rastomas wrote: For a L,R, and center set-up, run a wire from the positive of each side to the center speaker ( one to the pos lead, one to the neg lead. No neg wire involved).. This will give you the "stereo difference" to the center speaker. It will work best with the balance control in the middle.
For a front/rear ( or four-speaker) set-up, you can take the positives off of the rear channels and feed them to the center.
You will still get the stereo difference, and the center speaker is controlled by the fader.

I have done this many times. It is best with LIVE recorded music, tho.
Really fills out the sound.

Hafler Matrix.

I design and build audio gear, and have a few ways to do this at line level, but it's a neat trick on some amps and stereos to get that immersive feeling to the sound. Many old jukeboxes did this as well to get a more lively and full immersive experience. Works pretty well. Great for 70's and 80's recordings usually from live venues .

Funny you should mention old jukeboxes, I only know it's possible To daisy chain (I know it's not a real daisy chain) speakers like this because I had to learn how to wire this amplifier from an old jukebox!! See the old speaker configuration conversion. Chart. You can basically hook as many speakers to this thing as you want as long as you wire it correctly.